1. Field of the Invention
The present invention relates to a hard disk drive including a pivot assembly bearing device, and a pivot assembly bearing device.
2. Description of the Related Art
Hard disk drives are conventionally known, which have a pivot assembly bearing device configured to support a swing arm having a magnetic head for recording and reproducing signals. FIG. 12 is a cross-sectional view of a configuration of a conventional pivot assembly bearing device. As illustrated in FIG. 12, the conventional pivot assembly bearing device 100 has a configuration in which a cylindrical sleeve 101 relatively rotatably supports a cylindrical shaft 103 through a pair of axially-spaced rolling bearings 102 each including an inner race 102a, an outer race 102b, and rolling bodies 102c. The pivot assembly bearing device 100 having such a configuration fixes the shaft 103 to a base member of a hard disk drive, fits the sleeve 101 into a mounting hole 104 formed in a swing arm and swingably supports the swing arm.
With recent increase in processing speed, and capacity and density of information recorded in hard disk drives, the distance between a magnetic head and a magnetic disk has been reduced, and even fine foreign matter which has not been so significant causes failure of the hard disk drives. Thus, it is increasingly important to maintain cleanliness in the hard disk drives. The rolling bearing uses lubricant, but out-particles are generated by gasification or microparticulation of the lubricant, and a technique for keeping the out-particles from reducing cleanliness in a hard disk drive is demanded. In consideration of such a background, a pivot assembly bearing device is proposed, which keeps out-particles from reducing cleanliness in a hard disk drive (e.g., see Japanese Patent Application Laid-open No. 2013-48005). In particular, a technique is proposed in which sealing plates 105 and 106 are disposed at an upper end portion of the sleeve 101 to form a labyrinth gap, and the out-particles are kept from scattering outside the pivot assembly bearing device 100, as illustrated in FIG. 12.
However, as a result of an extensive study, the inventors of the present invention have found that even if sealing performance of a single pivot assembly bearing device is improved, scattering of the out-particles outside the pivot assembly bearing device cannot be effectively suppressed. FIG. 13 is a schematic diagram illustrating airflow around the conventional pivot assembly bearing device. In the hard disk drives, airflow is generally generated around the magnetic disk with the rotation of the magnetic disk. As indicated by an arrow A1 in FIG. 13, airflow passing through the pivot assembly bearing device partially flows into the pivot assembly bearing device 100, from a gap between a cover member 107 of the hard disk drive and an axial end surface of the sleeve 101. Airflow flowing into the pivot assembly bearing device 100 is discharged from the pivot assembly bearing device 100 to the outside, as indicated by an arrow A2 in FIG. 13. Therefore, the out-particles retained in the pivot assembly bearing device 100 are scattered outside the pivot assembly bearing device 100 by this airflow, and the scattered particles reduce the cleanliness in the hard disk drive.